Analyte concentration determination in physiological fluids (e.g., blood or blood derived products such as plasma) is of ever increasing importance in today's society. Such assays find use in a variety of applications and settings, including clinical laboratory testing, home testing, etc., where the results of such testing play a prominent role in the diagnosis and management of a variety of disease conditions. Analytes of interest include glucose for diabetes management, cholesterol for monitoring cardiovascular conditions, and the like.
A common method for analyte concentration determination assays is based on electrochemistry. In such methods, an aqueous liquid sample is placed into a sample reaction chamber in a sensor, e.g., an electrochemical cell made up of at least two electrodes, i.e., a working electrode and a counter electrode, where the electrodes have an impedance that renders them suitable for amperometric or coulometric measurement. The component to be analyzed is allowed to react with a reagent to form an oxidizable (or reducible) substance in an amount proportional to the analyte concentration. The quantity of the oxidizable (or reducible) substance present is then estimated electrochemically and related to the analyte concentration in the sample.
A desirable attribute of all sensor elements is that they have a long shelf life—that is, the sensing characteristic of the sensor element does not change significantly between manufacture and use (i.e. during storage). However, when stored for long periods of time and/or in non-optimal storage conditions, e.g., high temperatures, high humidity, etc., the performance of sensors can degrade. For example, the accuracy of analyte concentration determinations made using such sensors can be reduced. It is an object of the present invention to overcome or ameliorate these and other disadvantages in the prior art.